Date: Tue, 12 Dec 2000 23:16:24 -0500 (EST) From: Bosko Milekic <bmilekic@technokratis.com> To: Alfred Perlstein <bright@wintelcom.net> Cc: net@freebsd.org Subject: Re: need mbuf generic free() hook Message-ID: <Pine.BSF.4.21.0012122312270.23680-100000@jehovah.technokratis.com> In-Reply-To: <20001212042447.E16205@fw.wintelcom.net>
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Alfred, You've brought this up before. This looks familiar to your earlier post(s) regarding how to "abuse m_ext." Mind you, I may be mistaken, but that would be because this isn't being made awfully clear. Earlier you talked about forcing a custom free routine to be called even in the case of mbuf clusters, and we devised a way. Are you suggesting now to have a custom free routine called when your mbuf is freed (i.e. even when it is a non-M_EXT mbuf?) If that's so, I would urge you to re-examine the code because doing something like that would be generally wrong. I say "generally" because I'm always open to exceptions, as you know. So please clarify. On Tue, 12 Dec 2000, Alfred Perlstein wrote: > Ok, so I'm trying to rid FreeBSD of the unp_gc() junk in uipc_usrreq.c > I just realized why I'm leaking file descriptors: > > Only mbufs with external storage can have a 'free' function, the > problem is that for the most part when passing a single fd I'm only > using a single mbuf to pass my data around, my ext_free routine is > probably never called, and on top of that I'm probably corrupting > my mbuf by using it when I shouldn't be. > > This is terrible, what should be a simple free() hook is now my > worst nightmare. A couple of options come to mind: > > a) always have a free hook, the extra if (m->m_freehook != NULL) > check can't be that expensive. > b) a macro to make an mbuf into an mbuf cluster that points to itself, > it should check to see if it has enough room to shuffle the data > and return an error if it can't accomidate both the data and the > expanded mbug header. > > I like 'a' but would be willing to deal with 'b' as we've never > had a need for this, although that would mean copying about the > size of an mbuf in the worst case when a subsystem needs this > facility. > > Suggestions? Comments? > > -- > -Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org] > "I have the heart of a child; I keep it in a jar on my desk." > > Bosko Milekic bmilekic@technokratis.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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